Interface Devices, Systems, and Methods for Use with Intravascular Pressure Monitoring Devices

ABSTRACT

Embodiments of the present disclosure are configured to assess the severity of a blockage in a vessel and, in particular, a stenosis in a blood vessel. In some particular embodiments, the devices, systems, and methods of the present disclosure are configured to provide FFR measurements over a length of a vessel of interest in a small, compact device that integrates with existing proximal and distal pressure measurement systems and does not require a separate power source.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and the benefit of U.S.Provisional Patent Application No. 61/790,755, filed Mar. 15, 2013,which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to the assessment of vesselsand, in particular, the assessment of the severity of a blockage orother restriction to the flow of fluid through a vessel. Aspects of thepresent disclosure are particularly suited for evaluation of biologicalvessels in some instances. For example, some particular embodiments ofthe present disclosure are specifically configured for the evaluation ofa stenosis of a human blood vessel.

BACKGROUND

A currently accepted technique for assessing the severity of a stenosisin a blood vessel, including ischemia causing lesions, is fractionalflow reserve (FFR). FFR is a calculation of the ratio of a distalpressure measurement (taken on the distal side of the stenosis) relativeto a proximal pressure measurement (taken on the proximal side of thestenosis). FFR provides an index of stenosis severity that allowsdetermination as to whether the blockage limits blood flow within thevessel to an extent that treatment is required. The normal value of FFRin a healthy vessel is 1.00, while values less than about 0.80 aregenerally deemed significant and require treatment. Common treatmentoptions include angioplasty and stenting.

Coronary blood flow is unique in that it is affected not only byfluctuations in the pressure arising proximally (as in the aorta) but isalso simultaneously affected by fluctuations arising distally in themicrocirculation. Accordingly, it is not possible to accurately assessthe severity of a coronary stenosis by simply measuring the fall in meanor peak pressure across the stenosis because the distal coronarypressure is not purely a residual of the pressure transmitted from theaortic end of the vessel. As a result, for an effective calculation ofFFR within the coronary arteries, it is necessary to reduce the vascularresistance within the vessel. Currently, pharmacological hyperemicagents, such as adenosine, are administered to reduce and stabilize theresistance within the coronary arteries. These potent vasodilator agentsreduce the dramatic fluctuation in resistance (predominantly by reducingthe microcirculation resistance associated with the systolic portion ofthe heart cycle) to obtain a relatively stable and minimal resistancevalue.

However, the administration of hyperemic agents is not always possibleor advisable. First, the clinical effort of administering hyperemicagents can be significant. In some countries (particularly the UnitedStates), hyperemic agents such as adenosine are expensive, and timeconsuming to obtain when delivered intravenously (IV). In that regard,IV-delivered adenosine is generally mixed on a case-by-case basis in thehospital pharmacy. It can take a significant amount of time and effortto get the adenosine prepared and delivered to the operating area. Theselogistic hurdles can impact a physician's decision to use FFR. Second,some patients have contraindications to the use of hyperemic agents suchas asthma, severe COPD, hypotension, bradycardia, low cardiac ejectionfraction, recent myocardial infarction, and/or other factors thatprevent the administration of hyperemic agents. Third, many patientsfind the administration of hyperemic agents to be uncomfortable, whichis only compounded by the fact that the hyperemic agent may need to beapplied multiple times during the course of a procedure to obtain FFRmeasurements. Fourth, the administration of a hyperemic agent may alsorequire central venous access (e.g., a central venous sheath) that mightotherwise be avoided. Finally, not all patients respond as expected tohyperemic agents and, in some instances, it is difficult to identifythese patients before administration of the hyperemic agent.

To obtain FFR measurements, one or more ultra-miniature sensors placedon the distal portion of a flexible device, such as a catheter or guidewire used for catheterization procedures, are utilized to obtain thedistal pressure measurement, while a sensor connected to a measurementinstrument, often called the hemodynamic system, is utilized to obtainthe proximal or aortic pressure measurement. Currently only largeexpensive systems or a combination of multiple devices connected to thedistal pressure wire and the hemodynamic system can calculate anddisplay an FFR measurement. In that regard, to calculate the FFR thesedevices require both the aortic or proximal pressure measurement and thecoronary artery or distal pressure measurement. Accordingly, thesesystems require the catheter lab's hemodynamic system to have a highlevel analog voltage output. “High level” in this context generallyimplies 100 mmHg/Volt output. Unfortunately, there are many hemodynamicsystems that don't provide a high level output. As a result, when usingthese hemodynamic systems, providing an FFR measurement is difficult ifnot impossible. Further, space in a typical catheter lab is extremelylimited. Consequently, devices that are large and located in thecatheter lab are disfavored compared to smaller derives, especially ifthe smaller device can provide much if not all of the functionality ofthe larger device. As a result, it is highly desirable to have a devicethat that can display FFR and yet is small and lightweight that can siton, or near, the patient bed and be easily read by the physician.

Further, most pressure measurement devices require an extra source ofpower like an AC adapter or wall plug. This adds to wire clutter andavailable medical grade AC outlets are not often available near thepatient bed. In addition, any device that uses AC power must undergostringent safety precautions to reduce patient risk due to leakagecurrents. Batteries are another alternative for power. But, batteriesmust be replaced, disposed of correctly and have a finite shelf life.

Further still, FFR measurements are traditionally made with the proximaland distal pressure sensing devices maintained at static locations(e.g., within the aorta and distal of a suspected stenosis, in someinstances) when the hyperemic agent is applied. Accordingly, theresulting FFR measurements provide data in the context of those staticpositions.

Accordingly, there remains a need for improved devices, systems, andmethods for assessing the severity of a blockage in a vessel and, inparticular, a stenosis in a blood vessel. In that regard, there remainsa need for improved devices, systems, and methods for providing FFRmeasurements that have a small, compact size (e.g., suitable forhand-held use), integrate with existing proximal and distal pressuremeasurement devices, and provide FFR measurements over a length of avessel of interest rather than at a single, static location.

SUMMARY

Embodiments of the present disclosure are configured to assess theseverity of a blockage in a vessel and, in particular, a stenosis in ablood vessel. In some particular embodiments, the devices, systems, andmethods of the present disclosure are configured to provide FFRmeasurements in a small, compact device that integrates with existingproximal and distal pressure measurement systems and provide FFRmeasurements over a length of a vessel of interest rather than at asingle point.

In one embodiment, an interface for intravascular pressure sensingdevices is provided. The interface comprises: a distal input configuredto receive a distal pressure signal from a distal pressure sensingdevice; a proximal input configured to receive a proximal pressuresignal from a proximal pressure sensing device; a pullback deviceconfigured to interface with a proximal portion of the distal pressuresensing device to cause translation of the distal pressure sensingdevice relative to the proximal pressure sensing device; a processorcoupled to the distal input, proximal input, and the pullback device,the processor configured to calculate a pressure differential betweenthe distal pressure and the proximal pressure based on the receiveddistal pressure signal and the received proximal pressure signalobtained as the pullback device translates the distal pressure sensingdevice relative to the proximal pressure sensing device; and a displayin communication with the processor and configured to display thepressure differential calculated by the processor including a relativeposition of the distal pressure sensing device to the proximal pressuresensing device associated with the calculated pressure differential. Insome embodiments, the distal input, distal output, proximal input,proximal output, and processor are secured to a housing. Further, insome instances the distal pressure sensing device is a pressure-sensingguide wire and the proximal pressure sensing device is apressure-sensing catheter configured for use with the hemodynamicsystem.

In another embodiment, a system for evaluating a vascular stenosis isprovided. The system comprises: a distal pressure sensing device sizedand shaped for insertion into human vasculature; a proximal pressuresensing device sized and shaped for insertion into human vasculature;and an interface, where the interface includes: a distal inputconfigured to receive a distal pressure signal from a distal pressuresensing device; a proximal input configured to receive a proximalpressure signal from a proximal pressure sensing device; a pullbackdevice configured to interface with a proximal portion of the distalpressure sensing device to cause translation of the distal pressuresensing device relative to the proximal pressure sensing device; aprocessor coupled to the distal input, proximal input, and the pullbackdevice, the processor configured to calculate a pressure differentialbetween the distal pressure and the proximal pressure based on thereceived distal pressure signal and the received proximal pressuresignal obtained as the pullback device translates the distal pressuresensing device relative to the proximal pressure sensing device; and adisplay in communication with the processor and configured to displaythe pressure differential calculated by the processor including arelative position of the distal pressure sensing device to the proximalpressure sensing device associated with the calculated pressuredifferential.

Additional aspects, features, and advantages of the present disclosurewill become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present disclosure will be describedwith reference to the accompanying drawings, of which:

FIG. 1 is a diagrammatic perspective view of a vessel having a stenosisaccording to an embodiment of the present disclosure.

FIG. 2 is a diagrammatic, partial cross-sectional perspective view of aportion of the vessel of FIG. 1 taken along section line 2-2 of FIG. 1.

FIG. 3 is a diagrammatic, partial cross-sectional perspective view ofthe vessel of FIGS. 1 and 2 with instruments positioned thereinaccording to an embodiment of the present disclosure.

FIG. 4 is a diagrammatic, schematic view of a system according to anembodiment of the present disclosure.

FIG. 5 is a diagrammatic, schematic view of a system according to anembodiment of the present disclosure.

FIG. 6 is a diagrammatic, schematic view of a system according to anembodiment of the present disclosure.

FIG. 7 is a diagrammatic, schematic view of an interface device of thesystem of FIG. 6 according to an embodiment of the present disclosure.

FIG. 8 is a diagrammatic, schematic view of a portion of the interfacedevice of FIG. 7 according to an embodiment of the present disclosure.

FIG. 9 is a diagrammatic, schematic view of a portion of the interfacedevice of FIG. 7 similar to that of FIG. 8, but illustrating anotherembodiment of the present disclosure.

FIG. 10 is a graphical representation of proximal and distal pressuremeasurements over time during a pullback of a pressure sensing deviceobtaining the distal pressure measurements according to an embodiment ofthe present disclosure.

FIG. 11 is a graphical representation of proximal and distal pressuremeasurements during the pullback of the pressure sensing deviceobtaining the distal pressure measurements as shown in FIG. 10, butillustrating the proximal and distal pressure measurements relative to adistance according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It is nevertheless understood that no limitation tothe scope of the disclosure is intended. Any alterations and furthermodifications to the described devices, systems, and methods, and anyfurther application of the principles of the present disclosure arefully contemplated and included within the present disclosure as wouldnormally occur to one skilled in the art to which the disclosurerelates. In particular, it is fully contemplated that the features,components, and/or steps described with respect to one embodiment may becombined with the features, components, and/or steps described withrespect to other embodiments of the present disclosure. For the sake ofbrevity, however, the numerous iterations of these combinations will notbe described separately.

Referring to FIGS. 1 and 2, shown therein is a vessel 100 having astenosis according to an embodiment of the present disclosure. In thatregard, FIG. 1 is a diagrammatic perspective view of the vessel 100,while FIG. 2 is a partial cross-sectional perspective view of a portionof the vessel 100 taken along section line 2-2 of FIG. 1. Referring morespecifically to FIG. 1, the vessel 100 includes a proximal portion 102and a distal portion 104. A lumen 106 extends along the length of thevessel 100 between the proximal portion 102 and the distal portion 104.In that regard, the lumen 106 is configured to allow the flow of fluidthrough the vessel. In some instances, the vessel 100 is a blood vessel.In some particular instances, the vessel 100 is a coronary artery. Insuch instances, the lumen 106 is configured to facilitate the flow ofblood through the vessel 100.

As shown, the vessel 100 includes a stenosis 108 between the proximalportion 102 and the distal portion 104. Stenosis 108 is generallyrepresentative of any blockage or other structural arrangement thatresults in a restriction to the flow of fluid through the lumen 106 ofthe vessel 100. Embodiments of the present disclosure are suitable foruse in a wide variety of vascular applications, including withoutlimitation coronary, peripheral (including but not limited to lowerlimb, carotid, and neurovascular), renal, and/or venous. Where thevessel 100 is a blood vessel, the stenosis 108 may be a result of plaquebuildup, including without limitation plaque components such as fibrous,fibro-lipidic (fibro fatty), necrotic core, calcified (dense calcium),blood, fresh thrombus, and mature thrombus. Generally, the compositionof the stenosis will depend on the type of vessel being evaluated. Inthat regard, it is understood that the concepts of the presentdisclosure are applicable to virtually any type of blockage or othernarrowing of a vessel that results in decreased fluid flow.

Referring more particularly to FIG. 2, the lumen 106 of the vessel 100has a diameter 110 proximal of the stenosis 108 and a diameter 112distal of the stenosis. In some instances, the diameters 110 and 112 aresubstantially equal to one another. In that regard, the diameters 110and 112 are intended to represent healthy portions, or at leasthealthier portions, of the lumen 106 in comparison to stenosis 108.Accordingly, these healthier portions of the lumen 106 are illustratedas having a substantially constant cylindrical profile and, as a result,the height or width of the lumen has been referred to as a diameter.However, it is understood that in many instances these portions of thelumen 106 will also have plaque buildup, a non-symmetric profile, and/orother irregularities, but to a lesser extent than stenosis 108 and,therefore, will not have a cylindrical profile. In such instances, thediameters 110 and 112 are understood to be representative of a relativesize or cross-sectional area of the lumen and do not imply a circularcross-sectional profile.

As shown in FIG. 2, stenosis 108 includes plaque buildup 114 thatnarrows the lumen 106 of the vessel 100. In some instances, the plaquebuildup 114 does not have a uniform or symmetrical profile, makingangiographic evaluation of such a stenosis unreliable. In theillustrated embodiment, the plaque buildup 114 includes an upper portion116 and an opposing lower portion 118. In that regard, the lower portion118 has an increased thickness relative to the upper portion 116 thatresults in a non-symmetrical and non-uniform profile relative to theportions of the lumen proximal and distal of the stenosis 108. As shown,the plaque buildup 114 decreases the available space for fluid to flowthrough the lumen 106. In particular, the cross-sectional area of thelumen 106 is decreased by the plaque buildup 114. At the narrowest pointbetween the upper and lower portions 116, 118 the lumen 106 has a height120, which is representative of a reduced size or cross-sectional arearelative to the diameters 110 and 112 proximal and distal of thestenosis 108. Note that the stenosis 108, including plaque buildup 114is exemplary in nature and should be considered limiting in any way. Inthat regard, it is understood that the stenosis 108 has other shapesand/or compositions that limit the flow of fluid through the lumen 106in other instances. While the vessel 100 is illustrated in FIGS. 1 and 2as having a single stenosis 108 and the description of the embodimentsbelow is primarily made in the context of a single stenosis, it isnevertheless understood that the devices, systems, and methods describedherein have similar application for a vessel having multiple stenosisregions.

Referring now to FIG. 3, the vessel 100 is shown with instruments 130and 132 positioned therein according to an embodiment of the presentdisclosure. In general, instruments 130 and 132 may be any form ofdevice, instrument, or probe sized and shaped to be positioned within avessel. In the illustrated embodiment, instrument 130 is generallyrepresentative of a guide wire, while instrument 132 is generallyrepresentative of a catheter. In that regard, instrument 130 extendsthrough a central lumen of instrument 132. However, in otherembodiments, the instruments 130 and 132 take other forms. In thatregard, the instruments 130 and 132 are of similar form in someembodiments. For example, in some instances, both instruments 130 and132 are guide wires. In other instances, both instruments 130 and 132are catheters. On the other hand, the instruments 130 and 132 are ofdifferent form in some embodiments, such as the illustrated embodiment,where one of the instruments is a catheter and the other is a guidewire. Further, in some instances, the instruments 130 and 132 aredisposed coaxial with one another, as shown in the illustratedembodiment of FIG. 3. In other instances, one of the instruments extendsthrough an off-center lumen of the other instrument. In yet otherinstances, the instruments 130 and 132 extend side-by-side. In someparticular embodiments, at least one of the instruments is as arapid-exchange device, such as a rapid-exchange catheter. In suchembodiments, the other instrument is a buddy wire or other deviceconfigured to facilitate the introduction and removal of therapid-exchange device. Further still, in other instances, instead of twoseparate instruments 130 and 132 a single instrument is utilized. Inthat regard, the single instrument incorporates aspects of thefunctionalities (e.g., data acquisition) of both instruments 130 and 132in some embodiments.

Instrument 130 is configured to obtain diagnostic information about thevessel 100. In that regard, the instrument 130 includes one or moresensors, transducers, and/or other monitoring elements configured toobtain the diagnostic information about the vessel. The diagnosticinformation includes one or more of pressure, flow (velocity), images(including images obtained using ultrasound (e.g., IVUS), OCT, thermal,and/or other imaging techniques), temperature, and/or combinationsthereof. The one or more sensors, transducers, and/or other monitoringelements are positioned adjacent a distal portion of the instrument 130in some instances. In that regard, the one or more sensors, transducers,and/or other monitoring elements are positioned less than 30 cm, lessthan 10 cm, less than 5 cm, less than 3 cm, less than 2 cm, and/or lessthan 1 cm from a distal tip 134 of the instrument 130 in some instances.In some instances, at least one of the one or more sensors, transducers,and/or other monitoring elements is positioned at the distal tip of theinstrument 130.

The instrument 130 includes at least one element configured to monitorpressure within the vessel 100. The pressure monitoring element can takethe form a piezo-resistive pressure sensor, a piezo-electric pressuresensor, a capacitive pressure sensor, an electromagnetic pressuresensor, a fluid column (the fluid column being in communication with afluid column sensor that is separate from the instrument and/orpositioned at a portion of the instrument proximal of the fluid column),an optical pressure sensor, and/or combinations thereof. In someinstances, one or more features of the pressure monitoring element areimplemented as a solid-state component manufactured using semiconductorand/or other suitable manufacturing techniques. Examples of commerciallyavailable guide wire products that include suitable pressure monitoringelements include, without limitation, the PrimeWire PRESTIGE® pressureguide wire, the PrimeWire® pressure guide wire, and the ComboWire® XTpressure and flow guide wire, each available from Volcano Corporation,as well as the PressureWire™ Certus guide wire and the PressureWire™Aeris guide wire, each available from St. Jude Medical, Inc. Generally,the instrument 130 is sized such that it can be positioned through thestenosis 108 without significantly impacting fluid flow across thestenosis, which would impact the distal pressure reading. Accordingly,in some instances the instrument 130 has an outer diameter of 0.018″ orless. In some embodiments, the instrument 130 has an outer diameter of0.014″ or less.

Instrument 132 is also configured to obtain diagnostic information aboutthe vessel 100. In some instances, instrument 132 is configured toobtain the same diagnostic information as instrument 130. In otherinstances, instrument 132 is configured to obtain different diagnosticinformation than instrument 130, which may include additional diagnosticinformation, less diagnostic information, and/or alternative diagnosticinformation. The diagnostic information obtained by instrument 132includes one or more of pressure, flow (velocity), images (includingimages obtained using ultrasound (e.g., IVUS), OCT, thermal, and/orother imaging techniques), temperature, and/or combinations thereof.Instrument 132 includes one or more sensors, transducers, and/or othermonitoring elements configured to obtain this diagnostic information. Inthat regard, the one or more sensors, transducers, and/or othermonitoring elements are positioned adjacent a distal portion of theinstrument 132 in some instances. In that regard, the one or moresensors, transducers, and/or other monitoring elements are positionedless than 30 cm, less than 10 cm, less than 5 cm, less than 3 cm, lessthan 2 cm, and/or less than 1 cm from a distal tip 136 of the instrument132 in some instances. In some instances, at least one of the one ormore sensors, transducers, and/or other monitoring elements ispositioned at the distal tip of the instrument 132.

Similar to instrument 130, instrument 132 also includes at least oneelement configured to monitor pressure within the vessel 100. Thepressure monitoring element can take the form a piezo-resistive pressuresensor, a piezo-electric pressure sensor, a capacitive pressure sensor,an electromagnetic pressure sensor, a fluid column (the fluid columnbeing in communication with a fluid column sensor that is separate fromthe instrument and/or positioned at a portion of the instrument proximalof the fluid column), an optical pressure sensor, and/or combinationsthereof. In some instances, one or more features of the pressuremonitoring element are implemented as a solid-state componentmanufactured using semiconductor and/or other suitable manufacturingtechniques. Currently available catheter products suitable for use withone or more of Siemens AXIOM Sensis, Mennen Horizon XVu, and PhilipsXper IM Physiomonitoring 5 and that include pressure monitoring elementscan be utilized for instrument 132 in some instances.

In accordance with aspects of the present disclosure, at least one ofthe instruments 130 and 132 is configured to monitor a pressure withinthe vessel 100 distal of the stenosis 108 and at least one of theinstruments 130 and 132 is configured to monitor a pressure within thevessel proximal of the stenosis. In that regard, the instruments 130,132 are sized and shaped to allow positioning of the at least oneelement configured to monitor pressure within the vessel 100 to bepositioned proximal and/or distal of the stenosis 108 as necessary basedon the configuration of the devices. In that regard, FIG. 3 illustratesa position 138 suitable for measuring pressure distal of the stenosis108. The position 138 is less than 5 cm, less than 3 cm, less than 2 cm,less than 1 cm, less than 5 mm, and/or less than 2.5 mm from the distalend of the stenosis 108 (as shown in FIG. 2) in some instances. FIG. 3also illustrates a plurality of suitable positions for measuringpressure proximal of the stenosis 108. In that regard, positions 140,142, 144, 146, and 148 each represent a position that is suitable formonitoring the pressure proximal of the stenosis in some instances. Inthat regard, the positions 140, 142, 144, 146, and 148 are positioned atvarying distances from the proximal end of the stenosis 108 ranging frommore than 20 cm down to about 5 mm or less. Generally, the proximalpressure measurement will be spaced from the proximal end of thestenosis. Accordingly, in some instances, the proximal pressuremeasurement is taken at a distance equal to or greater than an innerdiameter of the lumen of the vessel from the proximal end of thestenosis. In the context of coronary artery pressure measurements, theproximal pressure measurement is generally taken at a position proximalof the stenosis and distal of the aorta, within a proximal portion ofthe vessel. However, in some particular instances of coronary arterypressure measurements, the proximal pressure measurement is taken from alocation inside the aorta. In other instances, the proximal pressuremeasurement is taken at the root or ostium of the coronary artery. Insome instances, the proximal pressure measurement is referred to as theaortic pressure.

As will be discussed below, in some implementations instrument 130 ismoved through the vessel 100 while obtaining pressure measurements. Inthat regard, in some implementations the instrument 130 is initiallypositioned distal of a region of interest and then pull backed throughand across the region of interest. To facilitate movement of theinstrument 130 through the vessel, a proximal section of the instrumentis coupled to a pullback device and/or other actuator configured toimpart translational movement to the instrument 130 and, in particular,the at least one element of the instrument configured to monitorpressure within the vessel 100. In some implementations, the pullbackdevice is configured to move at least a portion of the instrument 130 ata continuous speed for a fixed distance (e.g., 5 cm, 10 cm, 15 cm, orotherwise) and/or time (e.g., 10 seconds, 20 seconds, 30 seconds, 40seconds, 50 seconds, 60 seconds, or otherwise). In otherimplementations, the pullback device is configured to move at least aportion of the instrument 130 in a step-wise manner (i.e., move for acertain distance/time and then stop for a certain amount of time). Insome instances, the timing of the step-wise movement is coordinated withthe patient's heartbeat. In that regard, as discussed below someimplementations of the present disclosure rely on diagnostic windowscorresponding to only a portion of the patient's heartbeat cycle.Accordingly, in some instances it is desirable to maintain theinstrument 130 in a fixed position for one or more heartbeat cyclesbefore moving the instrument 130 to a next position. However, in otherinstances the instrument 130 is moved continuously through the vessel,while still using only a portion of the patient's heartbeat cycle forthe diagnostic window. In some instances, the pullback device includessome features similar to one or more of the pullback devices disclosedin U.S. patent application Ser. No. 11/250,159, filed Oct. 12, 2005,which is hereby incorporated by reference in its entirety, the R100Pullback Device available from Volcano Corporation, the Trak Back® IIDevice available from Volcano Corporation, and/or the SpinVision®Pullback Device available from Volcano Corporation. To that end,generally the instrument 130 will not require rotation and, therefore,the components of such pullback devices configured to impart rotation onthe received instrument (or a part thereof) are omitted and/or disabledin some implementations.

Referring now to FIG. 4, shown therein is a system 150 according to anembodiment of the present disclosure. In that regard, FIG. 4 is adiagrammatic, schematic view of the system 150. As shown, the system 150includes an instrument 152. In that regard, in some instances instrument152 is suitable for use as at least one of instruments 130 and 132discussed above. Accordingly, in some instances the instrument 152includes features similar to those discussed above with respect toinstruments 130 and 132 in some instances. In the illustratedembodiment, the instrument 152 is a guide wire having a distal portion154 and a housing 156 positioned adjacent the distal portion. In thatregard, the housing 156 is spaced approximately 3 cm from a distal tipof the instrument 152. The housing 156 is configured to house one ormore sensors, transducers, and/or other monitoring elements configuredto obtain the diagnostic information about the vessel. In theillustrated embodiment, the housing 156 contains at least a pressuresensor configured to monitor a pressure within a lumen in which theinstrument 152 is positioned. A shaft 158 extends proximally from thehousing 156. A torque device 160 is positioned over and coupled to aproximal portion of the shaft 158. A proximal end portion 162 of theinstrument 152 is coupled to an interface 170. In particular, in someinstances the proximal end portion 162 is coupled to a pullback device171 of the interface 170. The pullback device 171 is incorporated into ahousing of the interface 170 in some instances. In other instances, thepullback device 171 is in a separate housing from the interface 170, butin communication with one or more electronic components of the interface170. Interface 170 is a patient interface module (PIM) in someinstances. In some instances, the pullback device 171 and/or adjacentcomponent of the interface 170 include electrical connectors tofacilitate communication of data and/or signals between the instrument152 and the interface 170. In some instances, the instrument 152communicates data and/or signals wirelessly with one or more componentsof the interface 170. In that regard, it is understood that variouscommunication pathways between the instrument 152 and the interface 170may be utilized, including physical connections (including electrical,optical, and/or fluid connections), wireless connections, and/orcombinations thereof.

The interface 170 is communicatively coupled to a processing system 172having a display 173. Accordingly, the interface 170 and any interveningconnections facilitate communication between the one or more sensors,transducers, and/or other monitoring elements of the instrument 152 andthe processing system 172. In that regard, it is understood that anycommunication pathway between the instrument 152 and the interface 170may be utilized, including physical connections (including electrical,optical, and/or fluid connections), wireless connections, and/orcombinations thereof. Similarly, it is understood that any communicationpathway between the interface 170 and the processing system 172 may beutilized, including physical connections (including electrical, optical,and/or fluid connections), wireless connections, and/or combinationsthereof. Accordingly, it is understood that additional components (e.g.,connectors, antennas, routers, switches, etc.) not illustrated in FIG. 4may be included to facilitate communication between the instrument 152,the interface 170, and the processing system 172.

The system 150 also includes an instrument 176. In that regard, in someinstances instrument 176 is suitable for use as at least one ofinstruments 130 and 132 discussed above. Accordingly, in some instancesthe instrument 176 includes features similar to those discussed abovewith respect to instruments 130 and 132. In the illustrated embodiment,the instrument 176 is a catheter-type device. In that regard, theinstrument 176 includes one or more sensors, transducers, and/or othermonitoring elements adjacent a distal portion of the instrumentconfigured to obtain the diagnostic information about the vessel. In theillustrated embodiment, the instrument 176 includes a pressure sensorconfigured to monitor a pressure within a lumen in which the instrument176 is positioned. In one particular embodiment, instrument 176 is apressure-sensing catheter that includes a fluid column extending alongits length. In such an embodiment, a hemostasis valve is fluidly coupledto the fluid column of the catheter, a manifold is fluidly coupled tothe hemostasis valve, and tubing extends between the components asnecessary to fluidly couple the components. In that regard, the fluidcolumn of the catheter is in fluid communication with a pressure sensorvia the valve, manifold, and tubing. In some instances, the pressuresensor is part of or in communication with a hemo system 174 having adisplay 175. In other instances, the pressure sensor is a separatecomponent positioned between the instrument 176 and the hemo system 174.In some instances, the hemo system 174 includes features similar tothose found in Siemens AXIOM Sensis, Mennen Horizon XVu, and PhilipsXper IM Physiomonitoring 5.

As shown, the hemo system 174 is in communication with the processingsystem 172 to facilitate the transfer of data and/or signals between thesystems. In particular, in some implementations data obtained byinstrument 152 is passed from processing system 172 to hemo system 174,while data obtained by instrument 176 is passed from hemo system 174 toprocessing system 172. To that end, in implementations where instrument152 is utilized to obtain pressure measurements at a point of interestor across a region of interest within a vessel and instrument 176 isutilized to obtain a reference pressure measurement (e.g., an aorticpressure measurement, in some instances), the combined data from theinstruments 152 and 176 can be utilized to calculate FFR and/or similarpressure ratio calculation. For example, in some instances FFR orsimilar pressure ratio calculation is determined for pressuremeasurements obtained during a pullback of the instrument 152 usingpullback device 171. In this manner, the resulting FFR or similarpressure ratio calculation provides an indication of severity of astenosis or lesion along the length of the vessel that the instrument152 has been moved through during the pullback. Such information can beutilized to determine an appropriate treatment plan, including thedetermination of the type(s) of treatment(s) to be applied and wheresuch treatment(s) should be utilized.

In some embodiments, the connection(s) between the instrument 152, theinterface 170, the processing system 172, and the hemo system 174includes a wireless connection. In some instances, the connection(s)includes a communication link over a network (e.g., intranet, internet,telecommunications network, and/or other network). In that regard, it isunderstood that the processing system 172 and/or hemo system 174 ispositioned remote from an operating area where the instrument 152 isbeing used in some instances. Having the connection(s) include aconnection over a network can facilitate communication between theinstrument 152 and the remote processing system 172 and/or remote hemosystem 174 regardless of whether the computing device is in an adjacentroom, an adjacent building, or in a different state/country. Further, itis understood that the communication pathway(s) is a secure connectionin some instances. Further still, it is understood that, in someinstances, the data communicated over one or more portions of thecommunication pathway(s) is encrypted.

It is understood that one or more components of the system 150 are notincluded, are implemented in a different arrangement/order, and/or arereplaced with an alternative device/mechanism in other embodiments ofthe present disclosure. Alternatively, additional components and/ordevices may be implemented into the system. Generally speaking, thecommunication pathway between either or both of the instruments 152, 176and the computing device 173 may have no intermediate nodes (i.e., adirect connection), one intermediate node between the instrument and thecomputing device, or a plurality of intermediate nodes between theinstrument and the computing device.

In some embodiments, the interface 170 includes a processor and randomaccess memory and is programmed to execute steps associated with thedata acquisition and analysis described herein. For example, in someembodiments the interface 170 is configured to receive and displaypressure readings from one or both of the instruments 152 and 176 and/orcalculate (and display) FFR or other pressure ratio based on thepressure measurements obtained from the instruments 152 and 176.Accordingly, in some instances the data obtained by instrument 176 ispassed through hemo system 174 and processing system 172 to interface170. However, as discussed below with respect to FIGS. 5 and 6, othersystems of the present disclosure allow the interface 170 to obtain thedata from instrument 176 more directly. It is understood that any stepsrelated to data acquisition, data processing, instrument control, and/orother processing or control aspects of the present disclosure, includingthose incorporated by reference, may be implemented by the interface 170using corresponding instructions stored on or in a non-transitorycomputer readable medium accessible by the computing device. In someembodiments, the interface 170 includes one or more processing and/orsignal conditioning features and/or associated components/circuitry asdescribed in U.S. Pat. No. 6,585,660, which is hereby incorporated byreference in its entirety.

In the illustrated embodiment of FIG. 4, the interface 170 includes ahousing 180. The housing 180 contains the electronic components of theinterface 170. Exemplary embodiments of electronic componentarrangements suitable for interface 170 are described below with respectto FIGS. 7-9. In some embodiments, the interface 170 is sized to behandheld and/or sized to be positioned on or near a patient bed (e.g.,attached to a bed rail or IV pole). In that regard, in some instancesthe interface 170 is similar in size to the SmartMap® PressureInstrument available from Volcano Corporation, which has housingdimensions of approximately 15.75 cm (6.3″) wide, 8.853 cm (3.54″) tall,and 4.48 cm (1.79″) deep. Generally, the interface 170 has a widthbetween about 5 cm and about 25 cm, a height between about 5 cm andabout 25 cm, and a depth between about 1 cm and about 10 cm.

The interface 170 also includes a display 182 and buttons 184. In thatregard, the display 182 is configured to display various diagnosticinformation such as distal pressure, proximal pressure, pressuredifferentials (including FFR), distal pressure waveforms, proximalpressure waveforms, and/or additional diagnostic parameters. In someembodiments, in order to conserve the amount of energy needed foroperation of the interface 170, the display 182 is a low-power display,such as a liquid crystal display. However, any type of visual displaymay be utilized, including color and/or monochromatic displays. In someinstances, the display 182 covers a majority of a front surface of thedisplay. In that regard, in some particular embodiments the display 182is a touchscreen. In such embodiments, the buttons 184 may be virtualbuttons (i.e., displayed on the touchscreen display 182), physicalbuttons, and/or combinations thereof. Generally, the buttons 184 areconfigured to facilitate configuration and operation of the interface170 and/or pullback device 171. It is understood that any number ofbuttons may be utilized and that buttons may be utilized for multiplefunctionalities and/or be dedicated to a single function. As a result,the interface 170 may include one or more virtual or physical buttonsconfigured to facilitate use of the interface in the manners describedherein. Further, in some instances, in addition to or in lieu of display182 the interface 170 includes a video output configured to sendvideo/display signals to a separate display device (e.g., display 173 ofthe processing system 172, display 175 of the hemo system 174, astandalone display, and/or a display integrated with another medicalsystem).

Referring now to FIG. 5, shown therein is a system 186 according toanother embodiment of the present disclosure. In that regard, FIG. 5 isa diagrammatic, schematic view of the system 186. The system 186includes many components and features similar to system 150 describedabove. Accordingly, the following description will focus on thedifferences of system 186. As shown, the interface 170 of system 186 iscommunicates directly with hemo system 174, rather than needing tocommunicate through processing system 172. To that end, in someinstances the interface 170 is configured to output pressuremeasurements obtained by instrument 152 to the hemo system 174. Theinterface 170 is also configured to output the pressure measurementsobtained by instrument 152 to the processing system 172. Further, insome instances the interface 170 is configured to receive pressuremeasurements obtained by instrument 176 from the hemo system 174. Insome instances, the interface utilizes the pressure measurementsobtained by the instruments 152 and 176 to make FFR or other pressureratio calculations, including during a pullback of instrument 152.Further, in some implementations the interface outputs the pressuremeasurements of instrument 176 received from hemo system 174 to theprocessing system 172.

Referring now to FIG. 6, shown therein is a system 188 according toanother embodiment of the present disclosure. In that regard, FIG. 6 isa diagrammatic, schematic view of the system 188. The system 188includes many components and features similar to systems 150 and 186described above. Accordingly, the following description will focus onthe differences of system 188. As shown, in the embodiment of FIG. 6 theinterface 170 is configured to interface with both instruments 152 and176. Accordingly, in some instances the interface 170 is configured tocommunicate data obtained by each of instruments 152 and 176 to theprocessing system 171, which is a hemo system in some implementations.To that end, in some instances the interface 170 includes differentoutputs to the processing system 171 for each of the instruments 152 and176. In other instances, the data for both instruments 152 and 176 aresent over a common, shared output from interface 170. Exemplaryimplementations of the interface 170 in accordance with the schematic ofsystem 188 are described below.

Referring now to FIG. 7, shown therein is a schematic of the interface170 according to an exemplary embodiment of the present disclosure. Inthat regard, the interface 170 includes an input connector 190associated with the pullback device 171 for receiving a proximal end ofinstrument 152. Accordingly, in some embodiments with an arrangementsimilar to that shown in FIG. 6, input connector 190 is configured toreceive the proximal end of the instrument 152 and facilitatecommunication of signals to and from a distal pressure sensing component191 of the instrument 152. The interface 170 also includes an outputconnector 192 configured to send a distal pressure signal to a distalpressure input 193 of a processing system 172, hemo system 174, or othercomputing device. Accordingly, in some embodiments with an arrangementsimilar to that shown in FIG. 6, output connector 192 is configured tosend the distal pressure signal to an input of processing system 172. Inthat regard, in some embodiments processing system 172 is a hemo systemand the distal pressure signal is modulated based on the hemo system'sexcitation voltage to provide a low level output of the distal pressuresignal to the hemo system. A low level output in this context istypically 5 μV/Vexc/mmHg, where Vexc is the excitation voltage. However,larger or smaller level outputs are used in some instances.

In some embodiments, the output connector 192 is also used to facilitateenergy harvesting from the processing system, hemo system, or otherpressure measuring system. In that regard, to eliminate the need for anadditional power supply within the interface 170, a power supply circuit220 extracts a small amount of power from the system's excitationvoltage associated with the distal pressure input 193. The power supplycircuit 220 converts the extracted energy into the power needed to runthe remaining circuitry of the interface 170. In some instances, thepower supply circuit 220 is configured to be the only power source usedto power the components of interface 170. Since the excitation signalcan be AC, positive or negative DC, and/or have various wave form shapesand voltages, the power supply circuit 220 must be able to accept theseand convert to a regulated power supply. In that regard, the voltageextracted from the excitation signal is converted to a regulated Vccvoltage to operate the low power circuitry using a buck or boostregulator depending on the input voltage. A current limiter minimizesdistortion to the system's waveform at the peaks. In some instances, thecurrent is limited to a level below the AAMI transducer limits as to becompatible with most hemo systems. In some instances, the system'sexcitation voltage meets the IEC 60601-2-34 standard. In somealternative embodiments, the power supply circuit is configured tointerface with a battery or other rechargeable power supply device thatcan be utilized to power the components of the interface. In somealternative embodiments, the power supply circuit is configured tointerface with an AC adapter that is to be plugged into a wall outlet inorder to provide power to the components of the interface.

The interface 170 also includes an input/output connectors 194 and 195for interfacing with a proximal pressure measurement system. In someparticular embodiments, the input/output connectors 194 and 195 areconfigured to work with a pressure monitoring device of a hemo statsystem. Generally, the input/output connector 194 is configured toreceive signals from a proximal pressure sensing component 196.Accordingly, in some embodiments with an arrangement similar to thatshown in FIG. 6, input/output connector 194 is configured to receivesignals from instrument 176, where the proximal pressure sensingcomponent 196 is a pressure sensing component associated with theinstrument 176. The input/output connector 195 is configured to send aproximal pressure signal to a proximal pressure input 197 of aprocessing system, hemo system, or other computing device. Accordingly,in some embodiments with an arrangement similar to that shown in FIG. 6,the input/output connector 195 is configured to send the proximalpressure signal to an input of computing device 173 over connection 178.

In the illustrated embodiment of FIG. 7, conductors 200 and 202 carrythe excitation signal to the proximal pressure sensing component 196. Anamplifier 204 is electrically connected to the conductors 200 and 202 asshown. The amplifier 204 is an operational amplifier in someembodiments. The excitation signal extracted by amplifier 204 is sent toa microprocessor 206. As will be discussed below, the excitation signalis utilized to evaluate the proximal pressure signals received from theproximal pressure sensing component 196.

In the illustrated embodiment of FIG. 7, conductors 208 and 210 carrythe proximal pressure signal from the proximal pressure sensingcomponent 196 back to the proximal pressure input 197 of the computingdevice. In that regard, an amplifier 212 is electrically connected tothe conductors 208 and 210 as shown. The amplifier 212 is an operationalamplifier in some embodiments. The amplifier 212 is configured tomonitor or sample the proximal pressure signal being supplied from theproximal pressure sensing component 196. The sampled proximal pressuresignal is then sent to the microprocessor 206. Accordingly, both theexcitation signal/voltage sampled from conductors 200 and 202 and theproximal pressure signal sampled from conductors 208 and 210 are fed tothe microprocessor 206. In some instances, the microprocessor 206calculates the proximal pressure based on the excitation signal voltage(Vexc), and the proximal pressure sensing component's output. In thatregard, the proximal pressure sensing component's output conforms to theAAMI standard of 5 uV/Vexc/mmHg in some instances. For an AC excitationsignal, the microprocessor 206 must measure the proximal pressure signalvoltage in synchrony with the excitation waveform. In some instances,rather than the low-level inputs described above, the proximal pressuresignal is received by the interface 170 as a high level signal. Forexample, the proximal pressure signal is a high level signal from aVolcano LoMap (available from Volcano Corporation) or from an externalhemo system.

In some embodiments, the input/output connectors 194 and 195 are alsoused to facilitate energy harvesting from the hemo system or otherpressure measuring system. In that regard, to eliminate the need for anadditional power supply within the interface 170, the power supplycircuit 220 may be connected to conductors 200 and 202 and utilized toextract a small amount of power from the hemo system's excitationvoltage for the proximal pressure sensing component 196 and convert itinto the power needed to run the remaining circuitry of the interface170. As noted above, when connected to the proximal pressure sensingside the power supply circuit 220 is still configured to extract powerfrom the excitation signal sent from the controller/computing devicesuch that the extracted power can be used to power the components ofinterface 170. Since the excitation signal can be AC, positive ornegative DC, and/or have various wave form shapes and voltages, thepower supply circuit 220 must be able to accept these and convert to aregulated power supply without distorting the waveform that continues onto the proximal pressure sensing component 196. This is necessary toavoid affecting the pressure measurements obtained by the proximalpressure sensing component 196. The voltage extracted from theexcitation signal is converted to a regulated Vcc voltage to operate thelow power circuitry using a buck or boost regulator depending on theinput voltage.

As noted above, the interface 170 is also configured to receive andprocess distal pressure signals from a distal pressure sensing component191 of instrument 152. In that regard, a signal conditioning portion 216of the interface 170 is in communication with input 190 that receivesthe distal pressure signal. Referring now to FIG. 8, shown therein is aschematic of a portion the interface 170 according to an exemplaryembodiment of the present disclosure. In particular, FIG. 8 shows aschematic of an exemplary embodiment of signal conditioning portion 216of the interface 170. In that regard, the signal conditioning portion216 is configured to condition signals received from the distal pressuremeasurement device. The signal conditioning portion 216 provides theexcitation and amplification required for the distal pressuremeasurement device's pressure sensors, Ra and Rb, which collective formdistal pressure sensing component 191 in some instances. In someimplementations, the signal conditioning portion 216 is incorporated aspart of the pullback device 171. In other implementations, the signalconditioning portion is adjacent to or spaced from the pullback device171.

Calibration coefficients provided by the distal pressure measurementdevice utilizing an EPROM in the device connector, for example, are readto adjust the gain, offset, and temperature sensitivity for the device.The read values are used to adjust the three Digital to AnalogConverters (DACs) 224, 226, and 228, in the distal pressure front endcircuitry 216 that control the gain, offset, and temperature (TC)compensation, respectively. The distal pressure signal is then digitizedwith an Analog to Digital Converter 230, ADC, and sent to themicroprocessor 206. The microprocessor 206 can then display the distalpressure, display a waveform of the distal pressure, or utilize thedistal pressure or the distal pressure waveform for additionalcalculations. For example, in some instances the microprocessor utilizesthe distal pressure and/or distal pressure waveform with the proximalpressure and/or proximal pressure waveform to calculate FFR, calculate apressure differential between the proximal and distal pressures,identify a suitable diagnostic window for performing a pressuredifferential calculation without administering a hyperemic agent to thepatient, calculate a pressure differential during the identifieddiagnostic window, and/or combinations thereof.

Referring now to FIG. 9, shown therein is a schematic of a portion theinterface 170 according to another exemplary embodiment of the presentdisclosure. In particular, FIG. 9 shows a schematic of an exemplaryembodiment of signal conditioning portion 216′ of the interface 170. Inthat regard, the signal condition portion 216′ is configured tocondition signals received from the distal pressure measurement device.The signal conditioning portion 216′ provides the excitation andamplification required for the distal pressure measurement device'spressure sensors, Ra and Rb, which collective form distal pressuresensing component 191 in some instances. The distal pressure signal fromthe pressure sensors, Ra and Rb, is digitized with a two-channel Analogto Digital Converter 230, ADC, and sent to the microprocessor 206 forthe gain, offset, and/or temperature compensation. Calibrationcoefficients provided by the distal pressure measurement deviceutilizing an EPROM 222 in the device connector, for example, are read toadjust the gain, offset, and/or temperature sensitivity for the device.The read values are used by the microprocessor 206 to control the gain,offset, and/or temperature compensation. Firmware within themicroprocessor is utilized to control these parameters in someinstances. The microprocessor 206 can then display the distal pressure,display a waveform of the distal pressure, or utilize the distalpressure or the distal pressure waveform for additional calculations.For example, in some instances the microprocessor utilizes the distalpressure and/or distal pressure waveform with the proximal pressureand/or proximal pressure waveform to calculate FFR, calculate a pressuredifferential between the proximal and distal pressures, identify asuitable diagnostic window for performing a pressure differentialcalculation without administering a hyperemic agent to the patient,calculate a pressure differential during the identified diagnosticwindow, and/or combinations thereof. Accordingly, the signalconditioning portion 216′ of FIG. 9 provides similar functionality tothe signal conditioning device 216 of FIG. 8, but without the need forthe three Digital to Analog Converters (DACs) 224, 226, and 228.

Referring again to FIG. 7, the interface 170 is also configured tooutput the distal pressure signal to an input 193 of a computing device.In that regard, the microprocessor 206 provides a digitized signal to anadditional set of DACs in the distal output circuitry 218 that modulatethe excitation of the hemo system to provide a proportional distalwaveform of the distal pressure voltage back to the hemo system throughoutput 192. In some embodiments, the scaled voltage returned is the sameas a standard proximal pressure transducer, 5 uV/Vexc/mmHg, per the AAMIstandards. The output stage 218 modulates the external excitation of thehemo system to provide a duplicate wave shape, or a DC voltage, scaledto 5 μV/Vexc/mmHg, per AAMI standards for aortic transducers of thedistal pressure for the hemo system. Accordingly, by outputting thedistal pressure signal through output 192 and the proximal pressuresignal through output 196, both proximal and distal pressures can thenbe observed on the hemo system's display using the hemo system'sstandard low-level inputs.

As noted above, the interface 170 uses the proximal and distal pressuredata received from the instruments to calculate and display informationthat can be useful in the evaluation of the vessel and, in particular,evaluation of a stenosis of the vessel. In some instances, the interfaceis configured to calculate and display FFR or other pressure ratio. Foran FFR measurement, the microprocessor first normalizes the distalpressure to the aortic pressure. The difference or ratio between thedistal and aortic pressures is utilized to determine FFR or pressureratio. Further, in some instances the FFR or pressure ratio iscalculated as at least the pressure sensing element of instrument 152 ismoved through the vessel. Accordingly, in some instances the FFR orpressure ratio is tracked relative to movement of the pressure sensingelement of instrument 152, for example, based on time or distance. Tothat end, information about the movement of the pressure sensing elementof instrument 152 relative to the vessel and/or instrument 176 isobtained based on the motion, and associated timing of such motion,imparted by the pullback device 171. By correlating the difference orratio between the two pressures to the movement associated with thepullback, a pressure ratio map or visual representation of the vesselcan be created. For example, FIG. 10 provides a graphical representationof proximal and distal pressure measurements over time during a pullbackof instrument 152 according to an embodiment of the present disclosure.FIG. 11 provides a graphical representation of the proximal and distalpressure measurements during the pullback of the instrument 152 of FIG.10, but illustrates the proximal and distal pressure measurementsrelative to a distance according to an embodiment of the presentdisclosure. The resultant FFR or pressure ratio data (and associatedpositional/timing information) is stored in memory for later retrievaland/or shown on a display in real time.

In some embodiments the interface 170 includes user-controlled buttons,such as buttons 184 shown in FIGS. 4-6. In one particular embodiment,one of the buttons causes the microprocessor to ‘normalize’ the distalpressure measurement to the proximal pressure measurement. This istypically performed with the pressure sensing components 191 and 196positioned in close proximity to one another within the patient suchthat they are subjected to similar pressures. In some instances, thiscalibration is performed proximal of the lesion and before the distalpressure sensing component 191 is advanced distally beyond the lesion.After the distal pressure sensing component 191 is placed beyond thesuspect lesion actuation of another button causes the microprocessor 206to calculate the ratio of the distal pressure to the proximal pressure,which provides an FFR value or pressure differential. In that regard, insome implementations the button is pressed by a user at a precise momentduring hyperemia based on observation of the proximal and distalwaveforms, which may be displayed on a separate device (e.g., a displayof the hemo system) or displayed on display 182 of interface 170.Alternatively, the determination of the appropriate moment for the FFRcalculation can be done automatically by the microprocessor 206. In thatregard, in some instances the FFR calculation is performed at a pointcoinciding with the peak difference between the distal and proximal(aortic) pressures. In some embodiments, a pressure differential iscalculated during a diagnostic window without application of a hyperemicagent, as discussed below. In such embodiments, the pressuremeasurements and/or the pressure differential may be displayedcontinuously. Further, in some instances a user-controlled button isutilized to start a pullback. In particular, actuation of theuser-controlled button initiates the pullback device 171. In someinstances, a single button is utilized to both initiate a pullbacksequence and cause the microprocessor 206 to calculate the ratio of thedistal pressure to the proximal pressure.

In some instances the interface 170 is configured to provide pressuremeasurements and/or pressure differentials based on evaluationtechniques as described in one or more of UK Patent ApplicationPublication No. GB 2479340 A, filed Mar. 10, 2010 and titled “METHOD ANDAPPARATUS FOR THE MEASUREMENT OF A FLUID FLOW RESTRICTION IN A VESSEL”,UK Patent Application No. GB1100137.7, filed Jan. 6, 2011 and titled“APPARATUS AND METHOD OF ASSESSING A NARROWING IN A FLUID FILLED TUBE”,U.S. Provisional Patent Application No. 61/525,739, filed on Aug. 20,2011 and titled “DEVICES, SYSTEMS AND METHODS FOR ASSESSING A VESSEL,”and U.S. Provisional Patent Application No. 61/525,736, filed on Aug.20, 2011 and titled “DEVICES, SYSTEMS, AND METHODS FOR VISUALLYDEPICTING A VESSEL AND EVALUATING TREATMENT OPTIONS,” each of which ishereby incorporated by reference in its entirety.

In some embodiments, the interface 170 is utilized to calculate anddisplay FFR in a traditional FFR procedure where the patient isadministered a hyperemic agent. In other embodiments, the interface 170is utilized to calculate a pressure differential similar to FFR (i.e.,the ratio of distal pressure to proximal pressure) but without the useof a hyperemic agent, including during a pullback in someimplementations. In that regard, a suitable diagnostic window for makingsuch calculations must be determined and/or identified to have a usefulmeasurement. The diagnostic window for evaluating differential pressureacross a stenosis without the use of a hyperemic agent in accordancewith the present disclosure may be identified based on characteristicsand/or components of one or more of proximal pressure measurements,distal pressure measurements, proximal velocity measurements, distalvelocity measurements, ECG waveforms, and/or other identifiable and/ormeasurable aspects of vessel performance. In that regard, various signalprocessing and/or computational techniques can be applied to thecharacteristics and/or components of one or more of proximal pressuremeasurements, distal pressure measurements, proximal velocitymeasurements, distal velocity measurements, ECG waveforms, and/or otheridentifiable and/or measurable aspects of vessel performance to identifya suitable diagnostic window.

In some embodiments, the determination of the diagnostic window and/orthe calculation of the pressure differential are performed inapproximately real time or live to identify the diagnostic window andcalculate the pressure differential. In that regard, calculating thepressure differential in “real time” or “live” within the context of thepresent disclosure is understood to encompass calculations that occurwithin 10 seconds of data acquisition. It is recognized, however, thatoften “real time” or “live” calculations are performed within 1 secondof data acquisition. In some instances, the “real time” or “live”calculations are performed concurrent with data acquisition. In someinstances the calculations are performed by a processor in the delaysbetween data acquisitions. For example, if data is acquired from thepressure sensing devices for 1 ms every 5 ms, then in the 4 ms betweendata acquisitions the processor can perform the calculations. It isunderstood that these timings are for example only and that dataacquisition rates, processing times, and/or other parameters surroundingthe calculations will vary. In other embodiments, the pressuredifferential calculation is performed 10 or more seconds after dataacquisition. For example, in some embodiments, the data utilized toidentify the diagnostic window and/or calculate the pressuredifferential are stored for later analysis.

In some instances, the diagnostic window is selected by identifying aportion of the cardiac cycle corresponding to a time period in which thechange in velocity (i.e., dU) fluctuates around zero. Time periods wherethe change in velocity is relatively constant and approximately zero(i.e., the speed of the fluid flow is stabilized) are suitablediagnostic windows for evaluating a pressure differential across astenosis of a vessel without the use of a hyperemic agent in accordancewith the present disclosure. In that regard, in a fluid flow system, theseparated forward and backward generated pressures are defined by:

${{P_{+}} = {{\frac{1}{2}\left( {{P} + {\rho \; c{U}}} \right)\mspace{14mu} {and}\mspace{14mu} {P_{-}}} = {\frac{1}{2}\left( {{P} - {\rho \; c\; {U}}} \right)}}},$

where dP is the differential of pressure, ρ is the density of the fluidwithin the vessel, c is the wave speed, and dU is the differential offlow velocity. However, where the flow velocity of the fluid issubstantially constant, dU is approximately zero and the separatedforward and backward generated pressures are defined by:

${P_{+}} = {{\frac{1}{2}\left( {{P} + {\rho \; {c(0)}}} \right)} = {{\frac{1}{2}{P}\mspace{14mu} {and}\mspace{14mu} {P_{-}}} = {{\frac{1}{2}\left( {{P} - {\rho \; {c(0)}}} \right)} = {\frac{1}{2}{{P}.}}}}}$

In other words, during the time periods where dU is approximately zero,the forward and backward generated pressures are defined solely bychanges in pressure.

Accordingly, during such time periods the severity of a stenosis withinthe vessel can be evaluated based on pressure measurements takenproximal and distal of the stenosis. In that regard, by comparing theforward and/or backward generated pressure distal of a stenosis to theforward and/or backward generated pressure proximal of the stenosis, anevaluation of the severity of the stenosis can be made. For example, theforward-generated pressure differential can be calculated as

$\frac{P_{+ {distal}}}{P_{+ {proximal}}},$

while the backward-generated pressure differential can be calculated as

$\frac{P_{- {distal}}}{P_{- {proximal}}}.$

In the context of the coronary arteries, a forward-generated pressuredifferential is utilized to evaluate a stenosis in some instances. Inthat regard, the forward-generated pressure differential is calculatedbased on proximally originating (i.e., originating from the aorta)separated forward pressure waves and/or reflections of the proximallyoriginating separated forward pressure waves from vascular structuresdistal of the aorta in some instances. In other instances, abackward-generated pressure differential is utilized in the context ofthe coronary arteries to evaluate a stenosis. In that regard, thebackward-generated pressure differential is calculated based on distallyoriginating (i.e., originating from the microvasculature) separatedbackward pressure waves and/or reflections of the distally originatingseparated backward pressure waves from vascular structures proximal ofthe microvasculature.

In yet other instances, a pressure wave is introduced into the vessel byan instrument or medical device. In that regard, the instrument ormedical device is utilized to generate a proximally originating forwardpressure wave, a distally originating backward pressure wave, and/orcombinations thereof for use in evaluating the severity of the stenosis.For example, in some embodiments an instrument having a movable membraneis positioned within the vessel. The movable membrane of the instrumentis then activated to cause movement of the membrane and generation of acorresponding pressure wave within the fluid of the vessel. Based on theconfiguration of the instrument, position of the membrane within thevessel, and/or the orientation of the membrane within the vessel thegenerated pressure wave(s) will be directed distally, proximally, and/orboth. Pressure measurements based on the generated pressure wave(s) canthen be analyzed to determine the severity of the stenosis.

There are a variety of signal processing techniques that can be utilizedto identify time periods where the change in velocity is relativelyconstant and approximately zero, including using a differential, firstderivative, second derivative, and/or third derivative of the velocitymeasurement are utilized. For example, identifying time periods duringthe cardiac cycle where the first derivative of velocity is relativelyconstant and approximately zero allows the localization of time periodswhere velocity is relatively constant. Further, identifying time periodsduring the cardiac cycle where the second derivative of velocity isrelatively constant and approximately zero allows the localization of atime period where acceleration is relatively constant and near zero, butnot necessarily zero.

While examples of specific techniques for selecting a suitablediagnostic window have been described above, it is understood that theseare exemplary and that other techniques may be utilized. In that regard,it is understood that the diagnostic window is determined using one ormore techniques selected from: identifying a feature of a waveform orother data feature and selecting a starting point relative to theidentified feature (e.g., before, after, or simultaneous with thefeature); identifying a feature of a waveform or other data feature andselecting an ending point relative to the identified feature (e.g.,before, after, or simultaneous with the feature); identifying a featureof a waveform or other data feature and selecting a starting point andan ending point relative to the identified feature; identifying astarting point and identifying an ending point based on the startingpoint; and identifying an ending point and identifying a starting pointbased on the ending point. Additional details of techniques forselecting a suitable diagnostic window are described in U.S. ProvisionalPatent Application No. 61/525,739, filed on Aug. 20, 2011 and titled“DEVICES, SYSTEMS AND METHODS FOR ASSESSING A VESSEL,” which is herebyincorporated by reference in its entirety. In that regard, it isunderstood that the interface 170 may be programmed to determine one ormore diagnostic windows based on the techniques described in the presentdisclosure, including those incorporated by reference, and/or includeone or more hardware features configured to identify one or morediagnostic windows based on the techniques described in the presentdisclosure, including those incorporated by reference.

Further, for a variety of reasons the proximal pressure measurements andthe distal pressure measurements received by the interface 170 are nottemporally aligned in some instances. For example, during dataacquisition, there will often be a delay between the distal pressuremeasurement signals and the proximal pressure measurement signals due tohardware signal handling differences between the instrument(s) utilizedto obtain the measurements. In that regard, the differences can comefrom physical sources (such as cable length and/or varying electronics)and/or can be due to signal processing differences (such as filteringtechniques). The resulting delay between the signals is between about 5ms and about 150 ms in some instances. Because individual cardiac cyclesmay last between about 500 ms and about 1000 ms and the diagnosticwindow may be a small percentage of the total length of the cardiaccycle, longer delays between the proximal and distal pressuremeasurement signals can have a significant impact on alignment of thepressure data for calculating a pressure differential for a desireddiastolic window of a cardiac cycle.

As a result, in some instances, it is necessary to shift one of theproximal and distal pressures relative to the other of the distal andproximal pressures in order to temporally align the pressuremeasurements. For example, a portion of the distal pressure measurementor proximal pressure measurement may be shifted to be temporally alignedwith a corresponding portion of the proximal pressure measurement ordistal pressure measurement, respectively, coinciding with thediagnostic window. While a shift of only a portion of the distal orproximal pressure measurement associated with the diagnostic window isutilized in some instances, in other instances all or substantially allof the proximal and distal pressures are aligned before the portionscorresponding to a selected diagnostic window are identified.

Alignment of all or portion(s) of the proximal and distal pressures isaccomplished using a hardware approach in some instances. For example,one or more hardware components are positioned within the communicationpath of the proximal pressure measurement, the distal pressuremeasurement, and/or both to provide any necessary delays to temporallyalign the received pressure signals. In some instances, these hardwarecomponents are positioned within the interface 170. In other instances,alignment of all or portion(s) of the proximal and distal pressures isaccomplished using a software approach. For example, a cross-correlationfunction or matching technique is utilized to align the cardiac cyclesin some embodiments. In other embodiments, the alignment is based on aparticular identifiable feature of the cardiac cycle, such as an ECGR-wave or a pressure peak. Additionally, in some embodiments alignmentis performed by a software user where adjustments are made to the delaytime of at least one of the proximal and distal pressures until thecardiac cycles are visually aligned to the user. A further technique foraligning the signals is to apply a synchronized timestamp at the pointof signal acquisition. Further, in some instances combinations of one ormore of hardware, software, user, and/or time-stamping approaches areutilized to align the signals.

Regardless of the manner of implementation, several approaches areavailable for the aligning the proximal and distal pressure measurementsignals. In some instances, each individual distal pressure measurementcardiac cycle is individually shifted to match the correspondingproximal pressure measurement cardiac cycle. In other instances, anaverage shift for a particular procedure is calculated at the beginningof the procedure and all subsequent cardiac cycles during the procedureare shifted by that amount. This technique requires little processingpower for implementation after the initial shift is determined, but canstill provide a relatively accurate alignment of the signals over thecourse of a procedure because the majority of the signal delay is due tofixed sources that do not change from patient to patient or within theprocedure. In yet other instances, a new average shift is calculatedeach time that the proximal and distal pressure signals are normalizedto one another during a procedure. In that regard, one or more timesduring a procedure the sensing element utilized for monitoring pressuredistal of the stenosis is positioned adjacent the sensing elementutilized for monitoring pressure proximal of the stenosis such that bothsensing elements should have the same pressure reading. If there is adifference between the pressure readings, then the proximal and distalpressure signals are normalized to one another. As a result, thesubsequently obtained proximal and distal pressure measurements are moreconsistent with each other and, therefore, the resulting pressuredifferential calculations are more accurate.

With the proximal and distal pressure measurements aligned, the pressuredifferential for the diagnostic window is calculated. In some instances,the pressure differential is calculated using average values for theproximal and distal pressure measurements across the diagnostic window.The pressure differential calculations of the present disclosure areperformed for a single cardiac cycle, in some instances. In otherinstances, the pressure differential calculations are performed formultiple cardiac cycles. In that regard, accuracy of the pressuredifferential can be improved by performing the pressure differentialcalculations over multiple cardiac cycles and averaging the valuesand/or using an analysis technique to identify one or more of thecalculated values that is believed to be most and/or least accurate.

One advantage of the techniques of the present disclosure foridentifying diagnostic windows and evaluating pressure differentials isthe concept of “beat matching”. In that regard, the proximal and distalwaveforms for the same cardiac cycle are analyzed together with noaveraging or individual calculations that span more than a singlecardiac cycle. As a result, interruptions in the cardiac cycle (such asectopic heartbeats) equally affect the proximal and distal recordings.As a result, these interruptions that can be detrimental to current FFRtechniques have minor effect on the techniques of the presentdisclosure. Further, in some embodiments of the present disclosure, theeffect of interruptions in the cardiac cycle and/or other irregularitiesin the data is further minimized and/or mitigated by monitoring thepressure differential calculations to detect these anomalies andautomatically exclude the impacted cardiac cycles.

In one particular embodiment, pressure differential is calculated on twosequential cardiac cycles and the individual pressure differentialvalues are averaged. The pressure differential of a third cycle is thencalculated. The average value of the pressure differentials is comparedto the average pressure differential using three cycles. If thedifference between the averages is below a predetermined thresholdvalue, then the calculated value is considered to be stable and nofurther calculations are performed. For example, if a threshold value of0.001 is used and adding an additional cardiac cycle changes the averagepressure differential value by less than 0.001, then the calculation iscomplete. However, if the difference between the averages is above thepredetermined threshold value, then the pressure differential for afourth cycle is calculated and a comparison to the threshold value isperformed. This process is repeated iteratively until the differencebetween the averages of cardiac cycle N and cardiac cycle N+1 is belowthe predetermined threshold value. As the pressure differential value istypically expressed to two decimal places of precision (such as 0.80),the threshold value for completing the analysis is typically selected tobe small enough that adding a subsequent cardiac cycle will not changethe pressure differential value. For example, in some instances thethreshold value is selected to be between about 0.0001 and about 0.05.

In some instances, the level of confidence calculation has differentthresholds depending on the degree of stenosis and/or an initialcalculated pressure differential value. In that regard, pressuredifferential analysis of a stenosis is typically based around a cutoffvalue(s) for making decisions as to what type of therapy, if any, toadminister. Accordingly, in some instances, it is desirable to be moreaccurate around these cutoff points. In other words, where thecalculated pressure differential values are close to a cut-off, a higherdegree of confidence is required. For example, if the cutoff for atreatment decision is at 0.80 and the initial calculated pressuredifferential measurement is between about 0.75 and about 0.85, then ahigher degree of confidence is needed than if the initial calculatedpressure differential measurement is 0.40, which is far from the 0.80cutoff point. Accordingly, in some instances the threshold value is atleast partially determined by the initial calculated pressuredifferential measurement. In some instances, the level of confidence orstability of the calculated pressure differential is visually indicatedto user via a software interface.

Because pressure differential can be calculated based on a singlecardiac cycle in accordance with the present disclosure, a real-time orlive pressure differential calculation can made while the distalpressure measuring device is moved through the vessel. Accordingly, insome instances the system includes at least two modes: asingle-cardiac-cycle mode that facilitates pressure differentialcalculations while moving the distal pressure measuring device throughthe vessel and a multi-cardiac-cycle mode that provides a more precisepressure differential calculation at a discrete location. In oneembodiment of such a system, the interface 170 is configured to providethe live pressure differential value until the distal pressure measuringdevice is moved to the desired location and a measurement button isselected and/or some other actuation step is taken to trigger themulti-cardiac-cycle mode calculation.

Persons skilled in the art will also recognize that the apparatus,systems, and methods described above can be modified in various ways.Accordingly, persons of ordinary skill in the art will appreciate thatthe embodiments encompassed by the present disclosure are not limited tothe particular exemplary embodiments described above. In that regard,although illustrative embodiments have been shown and described, a widerange of modification, change, and substitution is contemplated in theforegoing disclosure. It is understood that such variations may be madeto the foregoing without departing from the scope of the presentdisclosure. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the presentdisclosure.

What is claimed is:
 1. An interface for intravascular pressure sensingdevices, comprising: a distal input configured to receive a distalpressure signal from a distal pressure sensing device; a proximal inputconfigured to receive a proximal pressure signal from a proximalpressure sensing device; a pullback device configured to interface witha proximal portion of the distal pressure sensing device to causetranslation of the distal pressure sensing device relative to theproximal pressure sensing device; a processor in communication with thedistal input, proximal input, and the pullback device, the processorconfigured to calculate a pressure differential between the distalpressure and the proximal pressure based on the received distal pressuresignal and the received proximal pressure signal obtained as thepullback device translates the distal pressure sensing device relativeto the proximal pressure sensing device; and a display in communicationwith the processor and configured to display the pressure differentialcalculated by the processor including a relative position of the distalpressure sensing device to the proximal pressure sensing deviceassociated with the calculated pressure differential.
 2. The interfaceof claim 1, further comprising: a distal output configured to output thedistal pressure signal to a hemodynamic system in a format useable bythe hemodynamic system; a proximal output configured to output theproximal pressure signal to the hemodynamic system in a format useableby the hemodynamic system;
 3. The interface of claim 2, wherein thedistal input, distal output, proximal input, proximal output, andprocessor are secured to a housing.
 4. The interface of claim 3, whereinthe housing has a width between 5 cm and 25 cm, a height between 5 cmand 25 cm, and a depth between 1 cm and 10 cm.
 5. The interface of claim1, wherein the distal pressure sensing device is a pressure-sensingguide wire.
 6. The interface of claim 5, wherein the proximal pressuresensing device is a pressure-sensing catheter.
 7. The interface of claim1, wherein the processor is further configured to identify a diagnosticwindow for calculating the pressure differential, the diagnostic windowconsisting of a portion of a heartbeat cycle of a patient.
 8. The systemof claim 7, wherein the portion of the heartbeat cycle of the patient isselected at least partially based on one or more characteristics of theproximal pressure signal.
 9. The system of claim 7, wherein the portionof the heartbeat cycle of the patient is selected at least partiallybased on one or more characteristics of the distal pressure signal. 10.A system for evaluating a vascular stenosis, the system comprising: adistal pressure sensing device sized and shaped for insertion into humanvasculature; a proximal pressure sensing device sized and shaped forinsertion into human vasculature; and an interface comprising: a distalinput configured to receive a distal pressure signal from a distalpressure sensing device; a proximal input configured to receive aproximal pressure signal from a proximal pressure sensing device; apullback device configured to interface with a proximal portion of thedistal pressure sensing device to cause translation of the distalpressure sensing device relative to the proximal pressure sensingdevice; a processor in communication with the distal input, proximalinput, and the pullback device, the processor configured to calculate apressure differential between the distal pressure and the proximalpressure based on the received distal pressure signal and the receivedproximal pressure signal obtained as the pullback device translates thedistal pressure sensing device relative to the proximal pressure sensingdevice; and a display in communication with the processor of theinterface, the display configured to display the pressure differentialcalculated by the processor including a relative position of the distalpressure sensing device to the proximal pressure sensing deviceassociated with the calculated pressure differential.
 11. The system ofclaim 10, wherein the display is a touchscreen.
 12. The system of claim10, wherein the display is further configured to display the proximalpressure and the distal pressure.
 13. The system of claim 10, whereinthe interface further comprises a distal output configured to output thedistal pressure signal to a processing system in a format useable by theprocessing system.
 14. The system of claim 13, wherein the processingsystem is a hemodynamic system.
 15. The system of claim 13, wherein thedistal input, distal output, proximal input, and processor are securedto a housing.
 16. The system of claim 10, wherein the distal pressuresensing device is a pressure-sensing guide wire.
 17. The system of claim16, wherein the proximal pressure sensing device is a pressure-sensingcatheter.
 18. The system of claim 10, wherein the processor is furtherconfigured to identify a diagnostic window for calculating the pressuredifferential, the diagnostic window consisting of a portion of aheartbeat cycle of a patient.
 19. The system of claim 18, wherein theportion of the heartbeat cycle of the patient is selected at leastpartially based on one or more characteristics of the proximal pressuresignal.
 20. The system of claim 18, wherein the portion of the heartbeatcycle of the patient is selected at least partially based on one or morecharacteristics of the distal pressure signal.